Layered video coding is common in video coding standards such as MPEG-2, MPEG-4, H.263, scalable extension of MPEG-4 AVC, etc. By coding an input video sequence into different layers, layered video coding provides decoding applications and devices with direct access to different coded versions of the input video. FIG. 1 shows an exemplary layered coded video bitstream structure, wherein an original video data sequence has been coded into multiple different layers. In this example, the video has been coded into two layers. Each layer is coded to represent different respective qualities or resolutions as compared to the other layers in the structure. For example, and referring to FIG. 1(a), layer 0 represents a coded low resolution version of video data, and layer 1 represents a coded high resolution version of the same video data. In this scenario, when a decoding application desires to use a low resolution version of the video, the application accesses the bitstream of layer 0. Analogously, when the application desires to utilize a high resolution coded version of the video, the application accesses the layer 1 bitstream. In this manner, a decoding application can rely on characteristics of the layered video coded structure of FIG. 1(a) to obtain one or more coded versions of a same video sequence.
Based on layer-to-layer relationships in a layered coded video structure, the encapsulated layers are either independent of other layers in the structure (representing a “simulcast” structure) or dependent on other layers in the structure. That is, all of the layers in a structure either do not rely on inter-layer prediction, or all of the layers user inter-layer prediction. The simulcast scheme can optimize each layer's performance since each layer is independent. However, when all layers are required by a requesting application, the simulcast scheme is not efficient. This is because each layer respectively represents a same set of video signals, resulting in significant amounts of data redundancy across the various layers. On the other hand, layered video coding with inter-layer prediction can leverage inter-layer correlations across image frames to improve coding performance.
For purposes of exemplary illustration, FIG. 1(a) represents a layered coded video structure comprising layers that utilize inter-layer prediction, and FIG. 1(b) represents a simulcast-based layered coded video structure. Referring to FIG. 1(a)), the arrow from layer 0 to layer 1 indicates that the coding of layer 1 uses layer 0 as prediction. Correspondingly, layer 1 can be coded more efficiently as compared to a similarly situated layer that is based on the simulcast layered video coding scheme. However, a disadvantage of layered video coding with inter-layer prediction is that the low layer bitstream should always be sent to the decoder, even when the decoder only needs to generate the high layer video. So when all layers are required, inter-layer prediction provides superior coding performance. In contrast, when only one layer is required, the simulcast scheme provides better performance.